The structure of pyochelin will be elucidated by NMR spectroscopy of the intact compound followed by NMR spectroscopy, mass spectrometry, and amino acid analysis of the fragments of pyochelin obtained after acid hydrolysis. Radioactive precursors to the aromatic and amino acid portions of pyochelin will be added to cultures synthesizing pyochelin in order to substantiate the biosynthetic pathways used and to obtain radioactive pyochelin. Radioactive iron (55Fe) will be used to determine the kinetics of transport of iron using pyochelin as the siderophore. If pyochelin has also been efficiently labelled, the fate of pyochelin during transport may be determined. By measuring the numbers of viable P. aeruginosa in the peritoneum, liver, spleen and blood for 96 hours following infection, the growth of P. aeruginosa and the effects of pyochelin upon growth will be determined. Pyochelin is toxic for mice and the extent of this toxicity will be determined. Clearance of bacteria from the bloodstream and the measurement of phagocytosis of bacteria by polymorphonuclear leucocytes and peritoneal macrophages from animals undergoing iron treatment will be used to determine the immunosuppressive effects of iron administration. Pyoverdin and pyocyanin will be included in the experiments on 55Fe transport in order to determine functional roles in iron metabolism. The structural elucidation of pyoverdin will concentrate on the single aromatic compound generated by acid hydrolysis of purified pyoverdin. Experiments will continue to be conducted on clinical isolates from the burn unit to determine any correlation of iron-sequestering ability and virulence in P. aeruginosa.